Question: If $a + b = -9$ and $x + y + z = -2$, what is $-2x + 9a + 9b - 2z - 2y$ ?
Explanation: $= 9a + 9b - 2x - 2y - 2z$ $= (9) \cdot (a + b) + (-2) \cdot (x + y + z)$ $= (9) \cdot (-9) + (-2) \cdot (-2)$ $= -81 + 4$ $= -77$